1. Field
The present invention relates generally to fifth wheel hitches for coupling trailers to tractor trucks, and, in particular, fifth wheel hitches having adjustable positions, and further, to slide rail assemblies for fifth wheel hitches.
2. Description of the Related Art
Fifth wheel hitches for towing a trailer behind a towing vehicle have long been known in the art. Examples of fifth wheel hitches include those disclosed in U.S. Pat. Nos. 4,721,323, 5,449,191, and 5,707,070.
Large over-the-road freight trailers are usually coupled to trucks by means of a fifth wheel assembly whereby the truck rear drive axles directly support a portion of the trailer load burden. Usually, the fifth wheel couple and support point is located along the length of the tractor between the rear drive wheels and the front steering wheels thereby distributing the front trailer load. It is desirable for the fifth wheel coupling to be adjustable in the longitudinal position with respect to the truck to aid in control over distribution of the load.
Typically, a fifth wheel hitch includes a support frame for mounting the hitch to the towing vehicle, such as, for example, to a tractor truck. This support frame includes a pair of base rails that are bolted to the bed and/or frame of the truck, side brackets that are releasably mounted to the base rails and a head support mounted to the side brackets. A head assembly is mounted to the head support by means of a trunnion arrangement allowing for pivotal fore-and-aft movement. The head assembly includes a jaw assembly specifically adapted to releasably engage and hold a kingpin of a trailer desired to be towed by the towing vehicle.
Fifth wheel hitches tend to be adjustable axially with respect to the tractor frame. One way of achieving this feature is attach slide rails to the support frame of the hitch and configure a pedestal, upon which the head assembly is pivotally mounted, to slidably engage the slide rails. The conventional design of these slide rails is nothing more than a flange extending inward of the slide assembly which may be angled metal. The rail is mounted to the support frame by fillet welding and by bolts.
However, the flange-type slide rail, since it is a single layer of material, provides only limited support to resist any upward loads. Further, the welding done to attach the rail to the support frame is time consuming, in addition to providing only a relatively weak attachment. Therefore, a need is identified for a slide to provide increased resistance to upward tending loads. A further need exists for such a slide rail to be manufactured in a reduced amount of time, but with greater strength of attachment to its support frame.